Chemical degradation of SiC/SiC composite for the cladding of gas-cooled fast reactor in case of severe accident scenarios

Effect of dissolved hydrogen on the corrosion behavior of chemically vapor deposited SiC in a simulated pressurized water reactor environment

“…They also have attractive properties regarding nuclear applications, including a low neutron absorption cross-section, low induced activation, and high resistance to neutron irradiation. Therefore, SiC has been considered for use in reactor cores for such as a constituent coating layer of tristructural-isotropic (TRISO) fuel particles and a control rod sheath as a form of the composite in very high temperature gas-cooled reactors, as well as for blanket structural materials and flow channel inserts in nuclear fusion reactors [5][6][7][8][9][10].…”

Initial assessment of environmental effects on SiC/SiC composites in helium-cooled nuclear systems

“…The conclusion of these studies 3,24,58,59 is that in order to withstand high temperatures for prolonged durations that may occur in severe accident scenarios, the SiC/SiC composites must be protected by thicker layers of β-SiC. Substitution of He (with 2 Pa O 2 ) by N 2 (with 0.5 Pa O 2 ) did not cause important differences in oxidation behavior of β-SiC (Fig.…”

“…The β-SiC coated SiC/PyC/SiC composite is a candidate for the cladding gas cooled fast reactor (GFR) and its chemical resistance in other environments that may develop in case of severe accident conditions was recently studied. 59 Figure 15 compares active oxidation weight loss rates of β-SiC and β-SiC-SiC/PyC/SiC composite in air, helium (with 2 Pa O 2 ) and in nitrogen (with 0.5 Pa O 2 ) at atmospheric pressure. The same three temperature domains were observed, which is not surprising.…”

“…13 The available sources contain very little information about the long term behavior of SiC/SiC composites in conditions simulating normal operation conditions of gas-cooled reactors. Recently published data 58,59 are targeted to GFR-relevant environments rather than VHTR. Long-term oxidation behavior studies in impure helium, both in irradiation-free and irradiation active conditions, are still needed.…”

“…Helium, with better thermal conductivity than nitrogen, allowed a lower final temperature (1725 o C) than nitrogen (2000 o C), but since nitrogen did not reduce the damage of β-SiC, the authors did not recommend replacing helium by nitrogen in the case of a sudden accidental loss of coolant. 59 The behavior of SiC/SiC composites in helium gas with higher oxygen content was studied experimentally to evaluate the suitability of SiC/SiC composites as candidate structural materials for fusion reactor blanket helium gas-cooled solid breeder blanket (HCSB) reactors. One recent study 60 addressed the difference in oxidation behavior between conventional composites with pyrolytic carbon interphase (PyC-SiC/SiC) and advanced multilayer interphase (ML-SiC/SiC) in He with 150 Pa O 2 at 1000 -1200 o C. The advanced ML-SiC/SiC composite showed small weight change at both 1000 and 1200 o C , while the conventional PyC-SiC/SiC composite behaved similarly only at 1200 o C. The good stability was due to SiO 2 which formed with relatively high rate and was able to seal the specimen surface and to protect the PyC interphase (passive oxidation).…”